docs: def change_port_speed(self, instance_id, public, speed):
          """Allows you to change the port speed of a virtual server's NICs.
  
          Example::
  
              #change the Public interface to 10Mbps on instance 12345
              result = mgr.change_port_speed(instance_id=12345,
                                          public=True, speed=10)
              # result will be True or an Exception
  
          :param int instance_id: The ID of the VS
          :param bool public: Flag to indicate which interface to change.
                              True (default) means the public interface.
                              False indicates the private interface.
          :param int speed: The port speed to set.
  
          .. warning::
              A port speed of 0 will disable the interface.
          """
          if public:
              return self.client.call('Virtual_Guest', 'setPublicNetworkInterfaceSpeed',
                                      speed, id=instance_id)
          else:
              return self.client.call('Virtual_Guest', 'setPrivateNetworkInterfaceSpeed',
                                      speed, id=instance_id)